Ice detector circuit

Abstract

An ice detector circuit for sensing an ice deposition on a sensing surface of an ice detector probe from an air mass flowing relative to the probe. The probe includes a heater to heat the sensing surface and a temperature sensor for sensing the sensing surface temperature during heating. The temperature sensor provides the circuit with an output having a level varying as a function of the sensing surface temperature. The circuit includes a controller which selectively energizes the heater, a timer which provides a timing output representative of a time interval elapsed between selected temperature sensor output levels, and computing means, such as a microprocessor, which computes an output representative of ice deposition as a function of a predetermined relationship between ice deposition and the timing output.

I claim: 
     
       1. An ice detector circuit for sensing an ice deposition on a sensing surface of an ice detector probe from an air mass moving relative thereto, the probe including heating means for heating the sensing surface to melt the ice deposition and sensing means for providing a sensor output having a level varying as a function of a temperature of the sensing surface, the circuit comprising: controller means coupled to the heating means for selectively energizing the heating means;   timing means coupled to the sensing means for providing a timing output representative of at least one interval of time elapsed between selected sensor output levels while the sensing surface is affected by heat from the heating means; and   computing means coupled to the timing means, said computing means having a conversion value representation of a predetermined relationship between the ice deposition and the elapsed time represented by the timing output, for providing an output representative of ice deposition on the sensing surface.   
     
     
       2. The circuit of claim 1, wherein the selective energization of the heating means provides heat at a controlled rate for melting the ice deposition, such that the timing output varies as a function of an amount of the ice deposition. 
     
     
       3. The circuit of claim 1, wherein the sensor output levels comprise a first sensor output level representing a lower timing threshold temperature and a second sensor output level representing an upper timing threshold temperature. 
     
     
       4. The circuit of claim 3, wherein the lower timing threshold temperature is not greater than the melting temperature of ice and the upper timing threshold temperature is greater than the melting temperature of ice, such that the timing output varies as a function of melting an ice deposition on the sensing surface. 
     
     
       5. The circuit of claim 1, wherein the controller means is further compiled to the sensing means to provide feedback, such that the selective deenergization of the heating means is a function of the temperature of the sensing surface. 
     
     
       6. An ice detector for providing an output representative of an ice deposition from an air mass moving relative thereto, comprising: an ice detector probe having a sensing surface for receiving the ice deposition and having heating means for heating the sensing surface to melt the ice deposition and having sensing means for providing a sensor output having a level varying as a function of a temperature of the sensing surface;   controller means coupled to the heating means for selectively energizing the heating means; and   timing means coupled to the sensing means for providing a timing output representative of at least one interval of time elapsed between selected sensor output levels, the timing output further representing the ice deposition, the selected sensor output levels comprising a first output which is a function of a temperature not greater than the melting of the ice to be detected and a second output which is a function of a temperature greater than the melting temperature of the ice to be detected.   
     
     
       7. An ice detector circuit for sensing an ice deposition on a sensing surface of an ice detector probe from an air mass moving relative thereto, the probe including heating means for heating the sensing surface to melt the ice deposition and sensing means for providing a sensor output having a level varying as a function of a temperature of the sensing surface, the circuit comprising: controller means coupled to the heating means for selectively energizing the heating means at a controlled rate for melting the ice deposition such that the sensor output varies as a function of an amount of ice deposition;   timing means coupled to the sensing means for providing a first timing output which is representative of a first interval of time during which ice can deposit on the sensing surface and a second timing output which is represented of a second interval of time during which the heating means melts the ice deposition; and   computing means coupled to the timing means, said computing means having a conversion value representative of a predetermined relationship between the ice deposition and the first and second timing outputs, for providing an output representative of ice deposition.   
     
     
       8. The circuit of claim 7, wherein the computing means further computes an output representative of a rate of ice deposition as a function of the first and second time intervals.